Pid Operation - Mitsubishi Electric MELSEC iQ-R Series User Manual

PID operation

The temperature control module can execute the process-value inexact differential PID control.
Operation method and operational expression
The process-value inexact differential PID control is an operation method in which a primary delay filter has been put on the
input of a derivative action and high-frequency noise has been eliminated to execute PID operations on the deviation (E).
■Algorithm of the process-value inexact differential PID control
The following figure shows the algorithm of the process-value inexact differential PID control.
Control response
parameters
Set value (SV) Slow
Normal
Fast
Proportional gain Derivative
K :
η:
P
Laplace transform
T : Integral time s:
I
T :
E: Deviation
Derivative time
D
■Operational expression
The following figure shows the operational expression of the temperature control module.
+
MV = K E + E + I
n P n n n-1
T
I
Deviation (SV-PV)
E:
:
Sampling cycle
MV:
PID control in process-value incomplete derivation output
Process value
PV:
Proportional gain
K :
P
T : Integral time
I
T : Derivative time
D
:
Derivative
I: Integral value
Derivative value
D:
The PID control in process-value derivation is an operation method in which the temperature process value
(PV) is used as a derivative term in a PID operation. No deviation is used for the derivative term, drastic output
changes due to a derivative action can be reduced when the deviation varies along with a set value change.
Temperature control module
+
-
T T
D D
D - PV - PV
n-1 n n-1
+ T
+ T
D
D
Disturbance D
+
1
K (1 + )
P
T · s
E -
I
Manipulated
value (MV)
K · T
P
1 + η · T
Controlled object
G(s)
· s
D
· s
D
Temperature
process value (PV)
APPX
Appendix 4 PID
A
335